Dilution Genes:
– Cream
– Dun
– Champagne
– Pearl
– Silver
Cream
Cream is what is known as an incomplete dominant, meaning that it expresses differently in its heterozygous and homozygous forms. Cream affects only red pigment in its heterozygous form, and effects black and red pigment in its homozygous form. There is a genetic test for cream and the designation for a heterozygous cream is CCr, and for a homozygous form is CrCr. A single cream dilute (heterozygous) has a 50% chance of passing on cream to its offspring and a double cream dilute (homozygous) has a 100% chance of passing on cream, regardless of the color of its mate.
Single Cream Dilutes:
Buckskin
A bay horse whose coat is diluted to a golden color, while the black pigment on the points is unaffected. The main body shade can vary from light to dark. They normally have dark skin and eyes. Occasionally, foals are born with blue eyes, and they are usually a dark or slate blue color, and normally darken with age. Some heavily diluted buckskins may appear to be almost silver, with minimal points or points diluted to a brown color. In these cases, a wild bay base coat is often suspected. Likewise, some buckskins appear very dark, with almost no dilution, and in these cases, a dark bay (seal or brown) phenotype is suspected. Buckskins and bay duns are easily mistaken for each other, and buckskins and Amber Champagne horses also share a similar phenotype.
Palomino
A red horse (chestnut) who is diluted to a golden shade over its entire body. They can be as dark as a true chestnut or appear almost white. They usually have a lighter (white, silver, or cream) mane and tail. Self-colored manes and tails occur, but this is rare. Their eyes and skin are usually dark, but some palominos never attain full pigmentation. They may be born with blue eyes that never fully darken, and pinkish skin which develops mottling or freckles. They are easily confused with the Gold Champagne phenotype.
Smokey Black
A black horse typically shows no signs of carrying cream. They may appear to fade badly or to be a chocolate color, with lighter eyes; however, these characteristics can also occur on black horses without cream. They are fully capable of producing cream dilute foals, and many breeders have been surprised when a palomino, buckskin, or double dilute foal is produced by a plain black horse.
Double Dilutes:
Perlino
A bay based horse who is completely diluted. They have a white to cream colored body and points, with pink skin and blue eyes.
Cremello
A chestnut based horse is turned a white to cream color, with a white or cream mane and tail. They have pink skin and blue eyes.
Smokey Cream
A black based horse is turned a cream color with a cream mane and tail. They have pink skin and blue eyes.
Dun
Dun effects both red and black pigment. Dun appears to lighten the base coat, but usually leaves the color of the mane, tail, and legs alone. Dun horses also show primitive markings, such as dorsal and shoulder stripes, and leg striping on the limbs, or various other parts of the body. This association is so strong and consistent, a horse is not believed to be dun unless they exhibit at least a dorsal stripe; nevertheless, not all horses with dorsal stripes or other primitive markings are dun. Primitive markings which occur on non-dun horses are considered a form of countershading. Foals frequently exhibit these markings and they usually disappear with the shedding of the foal coat. In some cases, the markings persist into adulthood. This may lead to confusion over whether a horse is dun or not. In many breeds, dun is also the traditional term for any yellow horse with dark points. This is particularly true outside of North America, and it is quite common for other dilution genotypes, particularly buckskin horses, to simply be called dun.
Issues like these have caused the dun genotype to be among the most confusing and the most difficult to correctly identify. In the past, it was done strictly on the basis of visual evidence, and/or by parentage or offspring. Currently, there is no direct test for dun, but UC Davis does offer a zygosity test, which is able to identify markers associated with the mutation in its hetero- and homozygous form. This test is not available for Spanish bred, Andalusian or Lusitano horses.
Dun is classified as a simple dominant mutation. An individual horse can have primitive markings and a diluted coat color, but this does not mean the horse is dun. One or both parents must also be dun. The breed of the horse should have documented evidence of dun or of a comparable dilution phenotype. The pedigree of the horse can be examined for evidence of dun, and if used for breeding, the offspring as well. Other color factors, such as sooty, gray, or cream, may obscure or prevent identification.
Dun is believed to be the oldest form of equine coloration, and the original wild color of the domestic horse. It is found in cave paintings, and in other equine species, such as the donkey and the wild ass. Przewalski’s Horse, the last living wild horse population, is exclusively bay dun in color.
Types Of Dun Are:
Bay Dun (Dun, Zebra Dun)
This is the most common type of dun. They usually have a tan body with black points, and often appear identical to buckskin horses, but with stronger primitive markings. Dun and cream can occur together, and when this happens, the horse may be called a dunskin.
Red Dun (Fox Dun)
A horse with a red (chestnut) base coat. The points are generally a shade darker than the main body, but the mane and tail may also be lighter. This color can be difficult to identify because the dilution and primitive markings may be subtle or not apparent. When it occurs with cream, the horse may be called a dunalino or linebacked palomino.
Black Dun (Grullo, Blue Dun, etc.)
A horse with a black base coat. They have black points and usually a darkened head (face mask). This is the rarest and most sought after form of dun and it is also very prone to misidentification. They are usually a grey color but have no relation to the color roan or to true grey. They can be nearly black, or a brown or grey-brown color. There are many different colloquial terms to describe shades of black dun.
Champagne
Champagne acts as a simple dominant gene. It dilutes the body and points of the horse. Champagne horses are born with bright blue eyes, brown hooves and pink skin. As they grow, pigmentation begins to appear in their eyes and skin. The eyes gradually darken, becoming blue-green and then an amber color with age. They can also stay blue-green or darken even further to a normal color. The pink skin develops freckles all over the body, and may tan and become darker with age. Foals are often darker when they are born, but when adult they do not lighten with further aging like grey does. Champagne horses often have an iridescent shine to the coat and may also display reverse dappling, but these traits occur on non-champagne horses as well. In the past, champagne horses were thought to be variants of cream or dun, but there is now a genetic test for champagne. The designation for a heterozygous champagne is N/Ch and for a homozygous champagne is Ch/Ch.
The Different Types of Champagne Are:
Amber Champagne
Bay based horses have a golden body, ranging in shades from light to dark, and with points from light brown to black. They can be mistaken for a buckskin.
Gold Champagne
Red (chestnut) based horses are shades of gold with a mane and tail color that ranges from white to the same color as the body (self colored). They often appear identical to palominos, and care must be taken not to confuse the two genotypes. Older champagne horses, whose eyes and skin have darkened, are especially prone to this mistake; and there are also some palomino horses who display a heavy dilution with lighter eyes or mottled skin.
Sable Champagne
The result of a dark bay, brown or seal phenotype, and not a classic bay.
Classic Champagne
Black based appears to be a sort of grey or chocolate metallic shade. They have dark points that may or may not be visible. They can be mistaken for a black dun color.
Pearl
The Pearl gene is also known as the “Barlink factor.” It resembles the champagne and cream genes but is neither. It is an incomplete recessive gene, with one copy doing nothing to the coat, while two copies will mimic champagne. When one copy of pearl and one copy of cream are present a pseudo double cream dilute color is the result. Many breeders theorize that pearl and cream are located at the same locus, meaning that a horse with both cream and pearl will only pass one or the other but not both to its offspring. Pearl has been located by UC Davis and they offer a test but they have not published their findings so we cannot at this time know for certain if this theory is correct.
Silver
Silver is a dilution that is believed to affect black pigment only. It generally dilutes the body and/or legs to a chocolate color or lighter, while the mane and tail usually dilute to a silvery/flaxen color. The roots of the hair often stay dark. Dappling may or may not appear in the coat and legs. Foals commonly have a wheat colored coat, white eyelashes and striped hooves, but these characteristics fade over time. Silver horses may become darker with age and lose much of the dilution in their mane and tails. Silver horses with the graying gene have been observed to gray faster than a horse without the silver gene.
Silver dapple was the original name for the phenotype, before it was realized that dapples did not always occur on all horses. Taffy is the name for silver in Australia. Silver is selectively bred for in the Rocky Mountain Horse and the color is called Chocolate, Chocolate Flax (if the mane and tail appear flaxen) or Red Chocolate. Silver is a dominant mutation, but it is still being investigated whether homozygous horses show more dilution than heterozygous horses. There is a genetic test for silver, and the designation for a heterozygous silver is N/Z and for a homozygous silver is Z/Z. The color remains relatively rare in the general horse population, but the number of breeds which have been confirmed to have Silver is growing.
The Two Types of Silver Are:
Black Silver (Silver Dapple)
A black horse with silver typically has a chocolate colored body, but they can range in shade from light grey to black in color. The mane and tail are usually a silver/flaxen color, but can also be a color similar to the base coat, or can appear sooty. The body commonly has dapples. They may be mistaken for flaxen liver chestnuts, or very sooty palominos. Look for the dark roots of the hair and at the lower legs, both areas which usually appear lighter in true chestnut horses.
Bay Silver
A bay horse will have diluted black points. A standard bay coat will be unaffected, but a dark bay horse may show dilution as well. The mane and tail are generally lighter, or a sooty silver color. The legs are usually diluted to a brown/grey color, often with mottling.